As a thought experiment, imagine a universe that was not explicable to its inhabitants, where the reasons why things happened were completely opaque and not open to human understanding. People there might say that ‘God works in mysterious ways’, that ‘mere mortals’ are not meant to understand God’s great master plan, hence we must have faith that the deity has his/her own reasons for everything, even if we can never comprehend them due to our limited perspective…

But wait! In our universe, that is exactly what traditional religionists say anyway! Therefore, theologians seem to be trying to have it both ways! The argument from explicability lacks refutability, because if the universe were not explicable they could argue that this too pointed to the existence of a deity.

Atheists have also pointed out that trying to explain the universe by invoking a deity is vacuous because it requires believing in something that cannot be explained, and hence is no explanation at all. I think this make Swiburne's claim particularly ironic. He seems to say: "We humans have an amazing ability to explain virtually the whole universe using science but we don't know why this is possible - it must be because something we can never hope to explain (God) exists after all." So if there is a God our ability to explain what's real ultimately fails. Such contradictory logic never ceases to amaze me.